Java 错误：抽象架构类型未知

我不明白为什么会出现这样的错误：

//EX[2,1,["java.lang.IllegalArgumentException/1755012560",
"An exception occurred while creating a query in EntityManager: 
\r\nException Description: Problem compiling [SELECT u FROM Users u]. \n[14, 19] 
The abstract schema type \x27Users\x27 is unknown."],0,7]

看起来所有的配置都是正确的，但我还是得到了这个错误。 请帮忙。我的配置如下：

MySql表：

CREATE TABLE `users` (
  `USER_ID` int(10) unsigned NOT NULL AUTO_INCREMENT,
  `USERNAME` varchar(45) CHARACTER SET utf8 COLLATE utf8_unicode_ci NOT NULL,
  `PASSWORD` varchar(45) CHARACTER SET utf8 COLLATE utf8_unicode_ci NOT NULL,
  `ENABLED` tinyint(1) NOT NULL,
  `firstname` varchar(50) CHARACTER SET utf8 COLLATE utf8_unicode_ci DEFAULT NULL,
  `lastname` varchar(50) CHARACTER SET utf8 COLLATE utf8_unicode_ci DEFAULT NULL,
  `email` varchar(50) CHARACTER SET utf8 COLLATE utf8_unicode_ci DEFAULT NULL,
  PRIMARY KEY (`USER_ID`)
) ENGINE=InnoDB AUTO_INCREMENT=3 DEFAULT CHARSET=utf8

package com.val.dogovora.entity;
import javax.persistence.*;
import java.io.Serializable;
@Entity
public class Users implements Serializable {
    @Id
    @GeneratedValue(strategy= GenerationType.IDENTITY)
    private int USER_ID;
    private String USERNAME;
    private String PASSWORD;
    private int ENABLED;
    private String firstname;
    private String lastname;
    private String email;

    public Users() {
    }
    public Users(String USERNAME, String PASSWORD, int ENABLED, String firstname, String lastname, String email) {
        this.USERNAME = USERNAME;
        this.PASSWORD = PASSWORD;
        this.ENABLED = ENABLED;
        this.firstname = firstname;
        this.lastname = lastname;
        this.email = email;
    }
Getters and Setters...
}

EntityManagerFactory emf = Persistence.createEntityManagerFactory("DogovoraPool");
EntityManager em = emf.createEntityManager();
TypedQuery<Users> query = em.createQuery("SELECT u FROM Users u", Users.class);

实体：

CREATE TABLE `users` (
  `USER_ID` int(10) unsigned NOT NULL AUTO_INCREMENT,
  `USERNAME` varchar(45) CHARACTER SET utf8 COLLATE utf8_unicode_ci NOT NULL,
  `PASSWORD` varchar(45) CHARACTER SET utf8 COLLATE utf8_unicode_ci NOT NULL,
  `ENABLED` tinyint(1) NOT NULL,
  `firstname` varchar(50) CHARACTER SET utf8 COLLATE utf8_unicode_ci DEFAULT NULL,
  `lastname` varchar(50) CHARACTER SET utf8 COLLATE utf8_unicode_ci DEFAULT NULL,
  `email` varchar(50) CHARACTER SET utf8 COLLATE utf8_unicode_ci DEFAULT NULL,
  PRIMARY KEY (`USER_ID`)
) ENGINE=InnoDB AUTO_INCREMENT=3 DEFAULT CHARSET=utf8

package com.val.dogovora.entity;
import javax.persistence.*;
import java.io.Serializable;
@Entity
public class Users implements Serializable {
    @Id
    @GeneratedValue(strategy= GenerationType.IDENTITY)
    private int USER_ID;
    private String USERNAME;
    private String PASSWORD;
    private int ENABLED;
    private String firstname;
    private String lastname;
    private String email;

    public Users() {
    }
    public Users(String USERNAME, String PASSWORD, int ENABLED, String firstname, String lastname, String email) {
        this.USERNAME = USERNAME;
        this.PASSWORD = PASSWORD;
        this.ENABLED = ENABLED;
        this.firstname = firstname;
        this.lastname = lastname;
        this.email = email;
    }
Getters and Setters...
}

EntityManagerFactory emf = Persistence.createEntityManagerFactory("DogovoraPool");
EntityManager em = emf.createEntityManager();
TypedQuery<Users> query = em.createQuery("SELECT u FROM Users u", Users.class);

persistence.xml

<class>com.val.dogovora.entity.Users</class>

com.val.dogovora.entity.Users

代码：

CREATE TABLE `users` (
  `USER_ID` int(10) unsigned NOT NULL AUTO_INCREMENT,
  `USERNAME` varchar(45) CHARACTER SET utf8 COLLATE utf8_unicode_ci NOT NULL,
  `PASSWORD` varchar(45) CHARACTER SET utf8 COLLATE utf8_unicode_ci NOT NULL,
  `ENABLED` tinyint(1) NOT NULL,
  `firstname` varchar(50) CHARACTER SET utf8 COLLATE utf8_unicode_ci DEFAULT NULL,
  `lastname` varchar(50) CHARACTER SET utf8 COLLATE utf8_unicode_ci DEFAULT NULL,
  `email` varchar(50) CHARACTER SET utf8 COLLATE utf8_unicode_ci DEFAULT NULL,
  PRIMARY KEY (`USER_ID`)
) ENGINE=InnoDB AUTO_INCREMENT=3 DEFAULT CHARSET=utf8

package com.val.dogovora.entity;
import javax.persistence.*;
import java.io.Serializable;
@Entity
public class Users implements Serializable {
    @Id
    @GeneratedValue(strategy= GenerationType.IDENTITY)
    private int USER_ID;
    private String USERNAME;
    private String PASSWORD;
    private int ENABLED;
    private String firstname;
    private String lastname;
    private String email;

    public Users() {
    }
    public Users(String USERNAME, String PASSWORD, int ENABLED, String firstname, String lastname, String email) {
        this.USERNAME = USERNAME;
        this.PASSWORD = PASSWORD;
        this.ENABLED = ENABLED;
        this.firstname = firstname;
        this.lastname = lastname;
        this.email = email;
    }
Getters and Setters...
}

EntityManagerFactory emf = Persistence.createEntityManagerFactory("DogovoraPool");
EntityManager em = emf.createEntityManager();
TypedQuery<Users> query = em.createQuery("SELECT u FROM Users u", Users.class);

EntityManagerFactory emf=Persistence.createEntityManagerFactory（“DogovoraPool”）；
EntityManager em=emf.createEntityManager（）；
TypedQuery query=em.createQuery（“从用户u中选择u”，Users.class）；

我想我找到了错误的原因。在我将我的项目从Eclipse转换为Intellij Idea之前。文件夹

my\u project\u name/war/web if/classes

保留在旧文件中。我删除了这个文件夹，现在我的项目没有任何错误。但我不明白，如果Intellij Idea有自己的文件夹，为什么要使用这些旧类